Backyard Aquaponics
A place to discuss aquaponics

Hi,

Right, I've been scouring the internet (and this forum) for all sorts of information on AP and I've sold the idea to my parents (I don't have my own garden) and shall be building a small/medium sized system to test it out. Then they've shown interest in building a full on 'family sustaining polytunnel job' if this works.....

I'd much rather have a CHIFT PIST system, but, due to space constraints, this medium sized system will have to only consist of a flood and drain 1 FT and several small growbeds.

The plan is to have a 112 gallon (454 liters) FT, : http://www.emsustains.co.uk/plastic_fish_ponds.htm (under rectangular tanks)

then a couple of these: http://www.podington.co.uk/planters-rai ... anter.html as GB's. They're 65 liters each, 80 cm long, 40cm wide and 35 cm high

Seeing as I haven't got a sump, when the water is pumped out of the FT the level will (obviously..) drop. So my question is, how many 65 liter GB's can I use in a F&D system with no sump. At what point are my fish (probably goldfish or trout if I can find some local to London) going to say 'Oi, this water is getting too f**king low!'.

Cheers,
Sonny

This will all depend on how many fish you plan on keeping in the tank. The more fish you have, the less the water you can pump out yet the more filtration you need. If you say pump out 1/3 of the water (about 150 liters) then you could fill about 300 liters of grow bed. That would be 4-5 of the 65 liter GBs. You will hear people say a prefered ratio is 2:1. That means twice as much GB volumn as FT. So idealy with a 120 gallon tank, you really want 240 gallons of GB. This can actually be achived with sequential filling of the grow beds. There are some home made sequencing valves you will find on here. Web4Deb has a youtube video of his and I have seen other around. RupertOfOz has a prefab one that he sells. IMO, his looks better then anything I could build.

Good Luck and welcome to the forum! I'm sure others will chime in to help.
Mark

Cheers Mark,

I'm trying to keep it as simple as possible for the first time round, think i'll stay away from sequencing valves for the moment.


I think 4 growbeds would be the best space-wise, so that's 260 liters of GB space. What number of/how many inches/kilos of trout would it take to support that GB space?

I assume that stocking at 'full capacity' (which I read is 1/2lb of fish per gallon) would be WAY too high for that ratio of GB:FT.

Thanks for your help,
Sonny

260 liters is about 60-70 gallons. Take half of that for FT valume so about 30 gallons for fish. At 1/2 lbs per gallon you could get 15 lbs of fish. Of course that is the grown out size. I would start with a dozen or so and cull when needed.

Can anyone else advise better as I am not that good with fish ratios???

Mark

I'm confused...

At the moment the hypothetical system has

FT: 112 Gallons

GB: 57 Gallons (4x14.25)


Is that ratio of FT:GB too high?

Yes - you have way more fish tank then grow bed. So you will have to stock lightly until you add more grow bed. You could also add some extra filtration. A 5 gallon bucket makes a pretty good swirl filter. Another option would be to add water changes to your weekly schedule.

Well the recommendation is to have 1:1 ratio or even better a 2:1 ratio (2 gb volume to 1 ft volume)... but in your case since you are experimenting it is still possible to keep your ratio... but you have to remember that it is the filtration (gb) volume that limits the amount of fishes you can keep, not the fish tank volume.

Check out the link below...
http://www.backyardaquaponics.com/forum/viewtopic.php?f=12&t=6646

In short, I think you can only keep about 4-5kg of fishes in that tank... depending on what fishes you choose to keep. For fishes that will eat smaller fishes then you are likely to get all these fishes grown out to plate size at the same time, hence you need to stock them at the fingerling stage assuming that they are at plate size weight...

For fishes that don't eat smaller fishes then you could stagger the harvest, so you could keep a variety of size amounting to 4-5kg...

Note that these figures are the maximum stocking figures of fishes... you can keep half these figures (ie. 2-3kg of fishes) and still get your AP to work well... in fact half stocking levels are better since there is more room for errors or things to go wrong before you lose all the fishes...

Hey, Sonny!

Right now I'm a bit , so take me even less seriously than normally....That said, here goes:

I just raised a dozen rainbow trout to nearly a foot in a 55 gal aquarium. Very nice learning experience as one can see their behavior very well. I've started harvesting them at 11.5". Half are smaller than 11", but they can grow some more. All have darkened noses from bumping glass, but seem quite healthy. We are using a 8CF (about 65gal) growbed and getting all the filtration we need. The sump is under the growbed, both of which are wood lined with 6mil LDPE (sold as visquine at our hardware stores). I figured the thing might rot out in a couple years, but so far so good.

Your 60gal growbed might take about 20gal from the FT. That should be ok. You might even get away with two growbeds (optimally with autosiphons so the typical drop in water level is less than with flood and drain, although max drop with be the same. Spider valve would be even better as the drop would never be more than about 1 growbed (20 gal).

I really, really, really like large fishtanks compared to the growbed and to the fish load. It allows you the peace of mind of knowing that if the power goes off or the pump fails that your fish will be fine for the many hours that it may take for rescue to arrive. Ignore my 55gal aquarium and heed my words. *grin* My other trout are in a 8000gal pool (25 trout...too few, but very happy. The algae gets all the nutes and the plants suffer) and an 800 gal stacked system (50 trout? Quite happy, and so are the plants, but the fish hide in the cave.)

Good luck, mate!
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Cheers guys, you're fantastic. I think a quick visit to the drawing board is needed... Expect me back in a day or two.....

Hows about a 100 gallon FT and one homemade (treated wooden frame with pond liner) 2m x 50cm x 30cm GB. That would be a 80 Gallon GB which, by hydrophilia's calculation, would take 26 gallons to flood.

So, remembering that I have no sump, this is a straight from FT > GB back to > FT operation, and the FT is only ever down by 26 gallons, 26%.

That means the fish are never down to an uncomfortable level right?

Hay there, sorry I didn't see this thread before.

You can have equal grow bed to fish tank ratio without needing a sump. So if you had a 100 gallon stock tank for fish tank and hooked it to a 100 gallon stock tank as a grow bed (provided you could support it high enough etc.) that would be fine. As long as you are stocking appropriate to the amount of grow bed!!!!!!

That would be 1 lb of final grow out weight of fish per 5 gallons of flood and drain gravel or in metric 3 kg of grown out fish per 100 liters of flood and drain gravel.

I personally like the idea of a 300 gallon fish tank and starting with 3, 100 gallon grow beds and if one later gets a sequencing valve they can add another 3, 100 gallon grow beds later. I just say 300 gallons cause it is the smallest fish tank I would want to raise a catfish to eating size in and 300 gallons is a good size to stabilize temperatures a bit. For a system that would feed a family, I would want at least 600-800 gallons of primary fish tank and 1200-1600 gallons of flood and drain gravel and probably about 600 gallons of sump tank. Then plan on adding a 100-300 gallon tank for quarantine of new fingerlings and a grow bed at least equal to the quarantine fish tank, this would want to be it's own system since it is for quarantine so you don't infect your big system with something that might come in with new fish. And I also have found need for something in the 20-50 gallon range for very small fingerlings or fry, this I have set up to be able to run as a system on it's own or I can connect it back into the bigger system for more stability.

Just some ideas. Anyway to repeat, you can have a 1:1 ratio system without a sump tank and still be ok, the water will fluctuate a bit but since you are not going to be stocking more fish than the grow bed can support, they shouldn't be too stressed by the fluctuations. If you do such a system with multiple grow beds on autosiphons, it will be rare that all grow beds will cycle together in which case the fluctuations will normally be even less extreme. Using a timer to get the flood and drain will provide the greatest water level fluctuations if not using a sump or an indexing valve.

Another option though it goes against the flood and drain favoritism we have here but that would be to have some gravel beds constantly flooded. Creative 1 does this and it seems to work well for him with trout. Some plants might be a bit more picky about wet feet and you would have to keep an eye on dissolved oxygen levels more (more aeration basically) but the flooded media method does offer more temperature stability and no water level fluctuations. Just gotta watch out for root rot but Creative 1 has done well with it.